This invention relates to a molding made up of a polyurethane foam molding having zones of different hardness and to a process for its production. This molding is particularly useful as a cushion for vehicle seats.
German Offenlegungsschrift No. 20 52 907 discloses a process for producing molded cushioning having areas differing in hardness in a single mold by using foams of different composition. The known processes were disadvantageous in that uncontrollable mixing resulted in flow of foamable reaction mixtures into and/or over one another. Such flow which results in hardening and waviness, made it impossible to achieve a reproducible distribution of hardness. German Offenlegungsschrift No. 20 52 907 resolved this difficulty by delimiting the individual zones from one another by means of textile fabrics or the like in the cavity of the mold, so that when the different reaction mixtures were introduced into the individual zones they were prevented from flowing into and/or over one another. The disadvantage of cushioning produced in this way is that the amount of material required for the inserts and the amount of time required for fixing the inserts in the mold cavity are both considerable and add to the cost of the moldings. Additionally, despite firm adhesion of the foam, these inserts which act as separating surfaces may form weak points along which the foam can split or tear. Such weak points will develop for example, when the cushioning is subjected to severe permanent stressing of the type to which motor vehicle, aircraft and ship seats are subjected.